From a quick look of the 2011 article (the second link), I was already aware of MP3 finally being unencumbered as that's one I'd been following since 2014 & is why I added back in LAME to WACUP after initially removing it to avoid potential issues whilst the patent was still in effect with earlier beta builds.
MPEG-2 seems to be viewed as having expired around mid-Feb 2018 though it's a bit hazy based on a quick search to validate that this is the case. It also doesn't have too much of an impact on Winamp/WACUP usage whereas it's more MPEG-4 that could be a possible issue (i.e. mp4/m4a containers) since that's still actively licensed from a quick look.
As for H.264, the article says "It will be a while before H.264 is patent free." though an alternative is to use
https://www.openh264.org/ (which covers the licensing via Cisco) &/or relying upon what the OS provides (if support is present). So technically it's possible to do H.264 without paying anything directly, just in-directly via OS purchases or reliance upon another organisation to do it on your behalf.
So you're mostly correct in the statement about not needing a pro license, not that it's hard to find a copy of it *cough*ProFit4Consumption.txt*cough* and from a WACUP view point, I've either replaced (or am replacing) most of the plug-ins that had a 'pro' control on them due to not being restricted on the MP3 side of things or just checking what the OS provides to enable other previously limited features.
Sadly there's still a lot of formats that definitely or potential require licensing though I doubt the scale of usership that Winamp/WACUP has/will have that it'll be an issue or things can be done (like I'm already doing) that just make it rely a bit more upon the OS provided features & the licensing costs that will have been paid via that

-dro